The present invention relates to apparatus and methods for preventing or inhibiting jackknifing of articulated vehicles and particularly relates to a passive damping constraint system for inhibiting an incipient jackknife condition while affording maneuverability during onset of a jackknife condition and further enabling automatic braking of the trailer in response to trailer speed in excess of tractor speed.
The present invention constitutes an improvement over the prior anti-jackknifing device set forth in my U.S. Pat. No. 4,385,772, dated May 31, 1983. In that patent, the fifth wheel and an accompanying rigid support member are mounted for pivotal movement on a rigid support structure secured to the frame of a tractor. The rigid support member includes side rails which mate with locating channels on the underside of the trailer when the trailer is coupled to the fifth wheel. Thus, the fifth wheel and accompanying rigid support member are mounted for rotation with the trailer relative to the tractor and about a generally vertical axis. The kingpin is, of course, mounted in the slotted arrangement of the fifth wheel. The fifth wheel and rigid support member, as shown in that patent, are mounted for rotation relative to the tractor through a braking system. By coupling the braking system between the trailer and the tractor to the conventional braking system of the articulated vehicle, the relative rotation of the tractor and trailer is prevented or inhibited each time the vehicle braking system is actuated.
While the anti-jackknifing device disclosed in my prior patent comprised a substantial improvement over then-known existing systems, it has been found in accordance with the present invention that a substantial part of the jackknifing problem in articulated vehicles relates to the failure to detect the onset of or an incipient jackknife condition as distinguished from normal trailer swings and transient responses for normal maneuvering of articulated vehicles, such as lane changes. Rather than responding to a jackknife condition, the present invention impedes or inhibits the oscillatory or yawing movement before the articulated vehicle obtains a predetermined angle indicative of an incipient jackknifing condition, whereas my prior patent and other devices respond, either manually or automatically, to actual jackknifing conditions. An incipient jackknifing condition may be defined as an articulation about a vertical axis of the trailer and tractor beyond a predetermined angle, for example, 10.degree.-12.degree. from straight-ahead centerline aligned positions of the trailer and tractor.
In accordance with the present invention therefor, there is provided a passive damping constraint system which will dampen and stabilize against trailer swings, i.e., oscillations or yaw, by a passive resistance to relative rotation between the tractor and trailer. By resisting the relative rotation about the vertical axis of the connection between the trailer and tractor, the rapidity of the yawing action and the speed of oscillations will be reduced. The maximum yawing angle under normal driving conditions will not occur as frequently using the passive damping constraint system hereof.
Further, the present invention not only inhibits the oscillatory and yawing relative motion of the trailer and tractor under normal driving conditions, but alerts the driver to an incipient jackknife condition, permitting the driver to maximize manual handling of the vehicle at the indicated onset of the jackknife condition. More particularly, a sensing system detects the relative angular alignment of the tractor and trailer from a predetermined alignment, (preferably the centerline alignment of the tractor and trailer with no angular deviation therebetween) and, upon obtaining a predetermined angular alignment, actuates a braking unit which will vigorously dampen and impede further angular displacement of the trailer relative to the tractor. Simultaneously, an alarm device, either audio or visual or both, coupled to the system will alert the driver to the incipient jackknife condition, affording the driver a manageable interval to react and manually control against the onset of a potential jackknife. If the driver reacts by applying the vehicle braking system, i.e., pressing the brake pedal, the present system is arranged, in response to application of vehicle braking, to deactivate the passive constraint system, as well as the fifth wheel braking system. This allows the driver full unimpeded manual control of the vehicle once alerted to the incipient jackknife condition. Upon manually restoring stability, the passive damping constraint system and the automatic fifth wheel braking system are automatically reactivated upon release of the vehicle brake pedal.
In another aspect of the present invention, the passive damping constraint system and fifth wheel braking system can be readily deactivated when normal vehicle maneuvering is required, such as docking the vehicle to a loading platform or the like. Thus, a master switch is provided in the circuitry of these systems operable by the vehicle driver so that these systems are shut down during normal maneuvers. Additionally, the systems may be deactivated during maneuvering on the road, for example, when changing lanes or turning corners. To accomplish this, the circuitry for actuation and deactuation of the passive damping constraint system and fifth wheel braking system includes normally closed switches which open upon actuation of the driver-operated turn signal. By opening the switches, the passive damping constraint and fifth wheel braking systems are deactivated, permitting the driver to change lanes under normal manual control. Once the lane change is effected and the turn signal returns to its normal position, the switches are closed to reactuate the passive damping constraint and fifth wheel braking systems.
As a further safety feature and means to prevent the development of further destabilizing forces acting on the articulated vehicle, it will also be appreciated that jackknifing sometimes occurs when trailer speed exceeds tractor speed. Thus, the trailer may overrun the tractor, causing a jackknife condition. To prevent this, the trailer kingpin is mounted to the trailer for a predetermined limited longitudinal movement relative to the trailer. Consequently, under normal pulling conditions, the tractor and trailer would be spaced a furthest distance one from the other. Switches are mounted in the rigid connecting structure along the underside of the trailer and are held normally open by their engagement with a rigid support member for mounting the fifth wheel. Should the trailer commence to overrun the tractor, the pin and slot move relative to one another (actually, the slot carried by the trailer moves forwardly relative to the pin), enabling the trailer mounted switches to be disengaged by the rigid support member mounting the fifth wheel. When these switches are disengaged, the switches close to automatically actuate the rear wheel braking system of the trailer to slow the trailer. This prevents a trailer-overspeed condition, which could result in a jackknife condition. When these switches close, an audible or visual alarm also alerts the driver to this overruning condition so that further preventative action can be taken by the driver. Upon braking the trailer, the trailer will move rearwardly relative to the tractor. The rigid support member mounting the fifth wheel will once again engage the switches and thereby deactuate the braking system for the rear wheels of the trailer.
In a preferred embodiment according to the present invention, there is provided apparatus for preventing a jackknife condition in an articulated vehicle, including a tractor and a trailer, comprising a tractor having a rigid support structure and a braking system, a support member rotatably carried by the rigid support structure for non-rotatable attachment to the trailer and a fifth wheel carried by the support member for rotation therewith. Means are provided interconnecting the support member and the rigid support structure for positively resisting relative rotation of the support member and the rigid support structure from an alignment thereof corresponding to a predetermined alignment of the tractor and trailer. Also provided are a switch for generating a signal in response to a predetermined angular rotation of the tractor and trailer relative to one another from the predetermined alignment thereof to an alignment indicative of an incipient jackknife condition and a brake for braking relative rotation of the support member and the rigid support structure in response to the signal.
In a further preferred embodiment according to the present invention, there is provided apparatus for preventing a jackknife condition in an articulated vehicle, including a tractor and a trailer, comprising a tractor having a rigid support structure and a braking system, a support member rotatably carried by the rigid support structure for non-rotatable attachment to the trailer, a fifth wheel carried by the support member for rotation therewith and a switch for generating a signal in response to a predetermined angular rotation of the tractor and trailer relative to one another from a predetermined rotational alignment thereof to an alignment indicative of an incipient jackknife condition. A brake is provided for braking relative rotation of the support member and the rigid support structure in response to the signal, with means for deactuating the brake in response to actuation of the tractor braking system thereby freeing the vehicle for manual control.
In a further preferred embodiment according to the present invention, there is provided a method for preventing a jackknife condition in an articulated vehicle comprising a tractor and a trailer, comprising the steps of passively resisting relative rotation of the tractor and the trailer from a predetermined alignment thereof, actuating a switch in response to a predetermined angular rotation of the tractor and trailer relative to one another from the predetermined alignment thereof to an alignment indicative of an incipient jackknife condition and applying a braking force to further resist relative rotation of the tractor and the trailer beyond the predetermined alignment thereof indicative of the incipient jackknife condition in response to actuation of the switch.
Accordingly, it is a primary object of the present invention to provide a novel and improved anti-jackknifing system for preventing the onset of a jackknife condition in an articulated vehicle wherein the system (i) automatically constrains the swinging or yawing oscillatory movement of the trailer relative to the tractor to inhibit an incipient jackknife condition, (ii) enables the driver of the vehicle to be alerted to the incipient jackknife condition, e.g., by visual or audible alarm, while simultaneously actuating the fifth wheel braking system to avert such condition, (iii) permits the driver once alerted to obtain full manual control over the vehicle by deactivating the passive damping constraint and fifth wheel braking systems in response to the application of brake pedal pressure and, subsequently, upon application of full brake pedal pressure, to reactuate the fifth wheel braking system, (iv) permits the driver to deactivate those systems during normal maneuvering on the road or docking and the like, and (v) prevents an overspeed condition of the trailer relative to the tractor which oftentimes leads to a jackknife condition.
These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.